The present invention relates to a cap of a liquid container such as a reagent container for use in a biochemistry analyzer and also to a device for opening and closing the cap.
Heretofore, there have been proposed various caps for liquid containers, as well as cap opening and closing devices. For example, as shown in FIG. 1, multiple pairs of liquid containers 1 are arranged on a container table 2 and a pair of caps can be simultaneously opened and closed by means of a cap opening and closing device secured to a disc plate 4. FIGS. 2A to 2C are plan, front and side views, respectively, showing one embodiment of a known cap opening and closing device. In those figures, a shutter 6 is arranged rotatably about a shaft 5 secured to the disc plate 4 and is energized in the direction of arrow A as shown in FIG. 2C by means of a spring 7 arranged around the shaft 5. A center portion of the shutter 6 is coupled with a leaf spring 9 by means of a connecting member 8. Both end portions 10, 11 of the leaf spring 9 are respectively connected to caps 14, 15 by means of connecting means 12, 13. Moreover, the shutter 6 has an arm portion 16 extending on an opposite side with respect to the caps 14, 15, and, as shown in FIG. 2C, a press member 17 is arranged to move forward and backward in the directions indicated by double headed arrows B and C by means of a drive means not show. Therefore, when the arm portion 16 is pressed by moving the press member 17 in the arrow B direction, the caps 14 and 15 can be removed from the liquid containers 1 by rotating the shutter 6 in an anti-clockwise direction about the shaft 5 against a force of the spring 7. When the press member 17 is moved in the arrow C direction, the caps 14 and 15 can be returned to an original position by means of the force of the spring 7. In this manner, cap opening and closing operations can be controlled by moving the press member 17 in the arrow B or C direction.
However, in the embodiment mentioned above, circular caps 14 and 15 are connected at the respective center portions thereof to the leaf spring 9 through the connecting means 12 and 13, and the center positions of the caps 14 and 15 are made identical with those of the liquid containers 1. Therefore, when the cap is removed from an opening defined by a mouthpiece 18 of the liquid container 1, the stress applied to the cap from the leaf spring 9 is almost uniform along the circular mouthpiece 18.
Moreover, in case of freezing the liquid container under the condition such that the opening of the liquid container is closed by the cap for preventing the liquid evaporation, there occurs a drawback that an inside pressure of the liquid container becomes a negative pressure state and thus the cap is tightly secured to the liquid container. Moreover, in an extreme case, the liquid contained in the liquid container is stuck to surfaces of the cap and the container, and thus the cap is adhered to the mouthpiece 18 of the liquid container. In this case, if the stress is applied to the arm portion 16 of the shutter by moving the press member 17 in the arrow B direction so as to remove the cap from the container, it is sometime impossible to remove the cap from the opening of the liquid container due to the negative pressure in the liquid container and an adhesive force between the cap and the liquid container.